Hemagglutinin (HA) of H9N2 influenza virus (HA)

Hemagglutinin (HA) is the primary surface glycoprotein of the H9N2 influenza virus and serves as a critical determinant of viral infectivity and host range [1, 8]. It is a Class I viral fusion protein that mediates the attachment of the virus to host cell sialic acid receptors and facilitates the fusion of the viral envelope with the endosomal membrane [1, 18]. The H9N2 subtype is endemic in poultry and is recognized as a significant zoonotic threat with pandemic potential, particularly as certain lineages have acquired mutations like Q226L that enhance binding to human-type receptors [13, 14]. HA is the major target of the host immune response and the primary component of both inactivated and recombinant vaccines [6, 15]. Therapeutic interventions targeting HA include neutralizing monoclonal antibodies and experimental small molecules, such as andrographolide derivatives, which aim to block viral entry or fusion [5, 7]. Continuous monitoring of HA antigenic drift and cleavage site mutations is essential for assessing pathogenicity and ensuring vaccine efficacy [9, 11].

Other names

HemagglutininHAH9 HAH9N2 HAViral surface glycoproteinH9N2 influenza virus Hemagglutinin antigen

Neutralization of viral entry by blocking receptor binding or preventing membrane fusion through stabilization of the prefusion HA structure [5, 7].